The present invention relates to palladium white gold alloys for the preparation of ring settings resistant to chemical or stress corrosion cracking, and methods of using such palladium white gold alloy free of platinum and nickel to form ring settings.
Few things can be as upsetting to a jeweler as having a customer return a ring due to prong failure. In some cases, the stone has fallen out and has been lost. This causes additional problems such as replacement cost, possible damage to the jeweler's reputation, and the likelihood of liability. Also, many pieces have sentimental value which cannot be restored by even the most skilled craftsman.
Having been approached with such problems in the past, we have conducted studies and metallurgical examinations under extreme magnification to establish the cause of the problem. These studies have indicated that the underlying cause of prong failure has frequently been due to residual stress. This is an internal condition within the metal which, if not relieved, leads to cracking and eventual failure of the prong.
The nickel white gold alloys are the most popular choices for diamond settings in the United States. While they look attractive, they have a tendency to create problems which lead to prong failure. Nickel, while acting as a whitening agent for gold alloys, can make the metal brittle. This is due to the nickel being insoluble with gold. As it is melted, it mixes with other base metals to form nickel rich boundaries which become brittle when stressed. Consequently, the whiter the alloy the more prone to brittleness it will be.
Most cracks are not visible to the naked eye. They are intergranular fractures which form along the grain boundaries of the metal itself. While cracking through some of the grains has been infrequently observed, the majority of these faults occur along the grain boundaries. Once they are formed, these cracks act as a conduit for corrosive elements which hasten prong failure.
The possibility of prong failure caused by stress related problems can occur during soldering, cutting the seat, and manipulation of the prong. Until now, the only two choices for white settings have been relatively inexpensive 14K nickel white gold or stronger platinum settings at a much higher price. The alloy described below minimizes the risk of prong shear loss associated with 14K nickel white gold alloys and offers the security of platinum without the high cost. Palladium is more forgiving, more malleable, and is easier to work with than nickel white gold, and is much less expensive than platinum. In fact, a 14K palladium white gold setting costs just a fraction more than a nickel gold setting.